This invention relates to low molecular weight interpolymers of a hydrophobic monomer, an ethylenically unsaturated carboxylic acid monomer or an ethylenically unsaturated dicarboxylic anhydride monomer and an alkenyl benzyl ether monomer, to water-soluble salts of such interpolymers, and to the use of such interpolymers and salts as dispersing agents for aqueous dispersions.
The dispersing of particulate matter in an aqueous medium has always presented the problem of obtaining suitable stability and flow characteristics for the various types of aqueous dispersions and for the various practical applications in which such dispersions are desirably employed. Accordingly, much effort has been expended in developing suitable aqueous dispersing agents for various purposes as is evidenced, for example, by the extensive collection of surfactant information summarized in McCutcheon's Detergents and Emulsifiers, North American Edition, 1973 Annual.
In spite of the extensive efforts of the prior art, many of the known dispersing agents are not suitable for many purposes, for example, by virtue of requiring high dispersing agent concentrations, by virtue of incompatibility with various coating composition ingredients, by virtue of limited storage stability of the resulting dispersions, etc. Moreover, there are certain particulate solids (notably certain especially difficult-to-disperse, finely divided inorganic pigments such as precipitated calcium carbonate and satin white and especially the high solids dispersions thereof) for which fully satisfactory dispersing agents have heretofore not been available.
In view of the foregoing deficiencies of the prior art, it is desirable to provide improved dispersing agents which are suitable for preparing aqueous dispersions of finely divided particulate matter (especially for high solids aqueous dispersions and particularly for high solids aqueous dispersions of finely divided inorganic solids such as precipitated calcium carbonate and satin white). Moreover, it is especially desirable to provide improved dispersing agents which furnish dispersions having improved storage stability and also which exhibit improved compatibility with aqueous polymer latexes such as those employed as film-forming components of coating compositions.